This invention relates to electric rotating machines and, particularly, to an AC alternator which optimizes magnetic flux coupling between a rotor and stator armature coils.
Because the linear velocity of a rotating rotor is greatest at its periphery or point of maximum radius, rotating machines have traditionally relied on the peripheral surface of the rotor for establishment of magnetic flux. This magnetic field, having the greatest linear velocity, is most effective to induce voltages in armature coils which are arranged in the stator to couple with the peripheral magnetic field of the rotor. However, what has not been fully appreciated is that the rotor also has axial surfaces which rotate as well and which, while these may be less effective, can provide a rotating magnetic field which, with suitably designed stator armatures can be instrumental to develop additional voltages.
The conventional alternator designs, which are based reliance on only peripheral magnetic flux fields, are necessarily limited in their efficiencies to the maximum amount of coupling between the peripheral rotor flux field and the armature coils arranged in the stator to couple with the peripheral flux field. While the peripheral flux field of the rotor is not restricted to the periphery and, some leakage flux exists in the regions of the axial surfaces of the rotor, such leakage of fluxes are merely incidental to the primary peripheral field and do not significantly increase the efficiency of the overall machine. Firstly, the leakage fluxes are generally weak fields. Secondly, and equally importantly, the stator designs are not such as to capitalize on the axial or lateral fields since no coupling mechanism was provided for coupling to these fields.